Tutorial "Build an MCP Server" does not work under zod v4

[Ranzeplay]

Describe the bug
Tutorial "Build an MCP Server" does not work under zod v4. No parameters accepted by the MCP server.

To Reproduce
Steps to reproduce the behavior:

1. Follow the tutorial to build a weather forecast MCP server
2. Run it and use an LLM to call it
3. Found that no interface accepts parameters

Expected behavior
Both interface should accept parameters

Logs

> echo '{"jsonrpc": "2.0", "id": 1, "method": "tools/list", "params": {}}' | node ./build/index.js
{"result":{"tools":[{"name":"get_alerts","description":"Get weather alerts for a state","inputSchema":{"type":"object","properties":{},"additionalProperties":false,"$schema":"http://json-schema.org/draft-07/schema#"}},{"name":"get_forecast","description":"Get weather forecast for a location","inputSchema":{"type":"object","properties":{},"additionalProperties":false,"$schema":"http://json-schema.org/draft-07/schema#"}}]},"jsonrpc":"2.0","id":1}

Additional context
Downgrade to zod v3 could solve the issue.

[oshimayoan]

Agree, I just experienced this with zod@4.0.15

[dashidhy]

Just use import { z } from "zod/v3" for the mcp and use v4 for the rest of your project.
modelcontextprotocol/typescript-sdk#555 (comment)

[jonathanhefner]

Hey, @Ranzeplay! 👋 Thank you for opening an issue!

The MCP TypeScript SDK v1.23.0+ supports both Zod v3 and v4 (see modelcontextprotocol/typescript-sdk#1040), so the tutorials should now also work with Zod v4.